Process of drying lumber



v F. K. FISH, JR.

PROCESS UF DRYING LUMBER.

APPLICATION FILED MAR. 22. 191 1. RENEWED DEC. 13. 1919.

1,328,658, Patented Jan. 20, 1920.

3 SHEETS-SHEET I.

F. K. FISH, JR-

PROCESS OF DRYING LUMBER.

APPLICATION FILED MAR- 22| I917- RENEWED DEC. 13,1919- 7 1,328,658, Patented Jan. 20, 1920.

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F. K. FISH, JR;

PROCESS OF DRYING LUMBER. APPLICATION FILED MAR. 22, 1911. RENEWED DEC. 13.1919. 1,328,658.

Patented J an. 20, 1920.

3 SHEETS-SHEET 3 UNITED STATES PATENT OFFICE.

FREDERICK K. FISH, JR., OF NEW YORK, N. Y., .ASSIG1\TOR T0 LUMBER TIE 8: TIMBER VULCANIZING COMPANY, OF NEW YORK, N. Y.

PROCESS OF DRYING- LUMBER.

Specification of Letters Patent.

Patented Jan. 20, 1920.

Application filed March 22, 1917, Serial No. 156,542. Renewed December 13, 1919. Serial No. 344,749.

To all whom it may concern:

Be it known that I, FREDERICK K. FISH, J12, a citizen of the United States, residing at 2 Stone street, New York city, in the county of New York and State of New York, have invented certain new and useful Improvements in Processes of Drying Lumber, of which the following is a specification.

The present invention is based upon a proper recognition of the physical characteristics of the structure of wood and analogous fibrous or porous substances, the chemical constituency of their fluid content and the possibility of converting into an agency for preservation, certain of their contained elements, which, under natural conditions, would form the basis of their deterioration or destruction, but refers more particularly to the treatment of the wood.

structurally, wood consists of a skeleton of cellulose intermingled with other organic substances, collectively designated as lignin, together with a minor proportion of mineral matter or ash. Lignin, while not fully understood chemically is closely allied to the cellulose material of the wood, and since it forms a part of the permanent structure of the wood, it may, for purposes of the present invention, be regarded identical with the cellulose.

To utilize the natural bases of resin, acetic acid and tannic acid, existing in wood, as preservatives of the Wood, it isnecessary that they be dislodged from their cellular confinement, separated from their aqueous solvent or vehicle, converted by oxidation and properly distributed through or deposited upon the cellular and fibrous structure of the wood.

The invention relates to the process of extracting from the wood the fluid content thereof, or such substances as may be developed therein during the operation of the process, and has for its object the drying of the wood proper and the collection therefrom of the fluids contained or developed therein during the process. Heretofore, it has been the practice to collect these fluids by means of distillation requiring the entire amount of fluids to be extracted by evaporation, and which requires a long and continuous supply of heat, which makes the process very expensive. In the process herein set forth, a great portion of the liquid content tain substances of the wood is forced out of the wood in an unevaporatcd state, which is due to the high temperature obtained by this process at the center of the wood piece, which forces the liquid content through the surface thereof in its liquid form, and which method, in some cases, results in the obtaining of certhat are not obtained through evaporation.

I am aware that certain patents have been obtained for drying wood with free steam, and heat under vacuum. By these methods wood may be dried but require such a length of time to accomplish an ideal and uniform product under such methods as to make them uncommercial, from a lumbermans viewpoint and cost such a large amount of money that such a process would not have any commercial value. If the time required to treat wood under such a process were reduced to a point where the methods would produce an amount of wood which would make it of interest to the lumber manufacturer, the heat in the sterilizer under the vacuum step would be of a degree that would cause the removal from the lumber of the preservatives of the wood, and therefore, decreases very materially the value of the wood. In addition to which, the shrinkage in the wood would be great and excessive and the wood would be rendered brittle and where in close contact with the heating coils, would be discolored. In the method herein specified, the vacuum step is for such a short length of time that only the surface moisture is removed and the resin and gums are distributed upon the fiber of the wood.

The release and conversion of these substances, especially the most important of them, namely, the volatile oils which. when oxidized, form resin, is accomplished, according to my invention, by racking the wood on a suitable truck or car, the individual pieces of the wood being spaced apart, the intervening spaces being filled with any substance which readily absorbs and radiates heat, such as gravel or metal; then placing the truck load of wood in a sweat'chamber and subjecting it to a moderately heated, moist atmosphere for a period of time, and then introducing it into a sterilizer capable of standing a high degree of internal heat and pressure. then introducing into the sterilizer free steam under pressure for a period of time, then lowering thepressure and wood piece.

temperature of the free steam, but maintaining a saturated condition thereof for a period of time, a partial vacuum being created around the Wood, the foregoing treatment having a tendency to open up the pores of the Wood and in a measure soften the fibers thereof which renders it more receptive to the super-heated water in the succeeding step; then introducing into the sterilizer super-heated water under pressure, preferably of about twenty pounds and of sufficient quantity to completely submerge the wood, for a sufficient period, usually about -one hour, to thoroughly open up the pores of the wood, dissolve its gummy sap matters that line its cellular tissues and put it into good physical condition to readily give up its aqueous content, without checking or other physical deterioration of the wood piece. A vacuum is now formed in the sterilizer which causes ready and free vaporization of the fluid content of the wood.

The wood naturally cools more slowly than the heat absorbing and radiating material, and therefore the process of the cooling of the wood is retarded by the radiation of the heat from said material. The aqueous contents of the wood are, or some of them, at a tem rature Well above the boiling point at t e existing pressure immediately before the vacuum is formed, which results in vaporization taking place from the center of the wood piece outwardly, and the internal pressure drives out of the wood the unvaporized liquid content. Any other suitable means for supplyin additional heat to the wood may be empl byed for the heat radiating material which will admit of the control of the pressure and moisture of the va or within the sterilizer. For instance, eat may be supplied to the sterilizer by steam circulated in steam coils. Proper saturation of the heating vapor is highly essential to the obtaining of satisfactory results. Variations of saturation are more or less controlled by the surface evaporation of the wood. This process results in the opening up and distending of the pores of the The products of evaporation are now withdrawn from the sterilizer and dry heat supplied therein by the circulation of steam through the heating coils until the desired temperature is obtained. to further evaporate any liquid content of the wood or rocure such chemical reaction as may be desired or to liquefy or volatilize other substances of the wood. Next, the wood is subjected to what I term the equalizing step which consists in placing the wood in an equalizing chamber. which is provided with heating pipes preferably located at the bottom; This equalizing chamber is further (provided with tracks for convenient intro. action of the charge of lumber, and

t a e p e e l We, 59 as W have a high co-etficient of heat insulation for the sake of economy of operation. The heat is circulated through pipes in the equalizing chamber. Finally, the wood is placed in a cooling chamber, said chamber preferably having insulated walls and the wood therein subjected to a moderately heated, moist atmosphere until the center of the wood piece and the surrounding atmosphere are harmonized. The wood will now be thoroughly dried without removing the values of its sap; the latter will be converted especially as to its volatile oils, into resin; this resin having permeated the entire cellular structure of the wood, while the moisture was still present and the pores opened up and temperature high. will have precipitated upon or surrounded the cell walls or fibers now that the moisture has departed. Thus, the wood has been rendered homogenous throughout, and so treated by its contained preservatives as to lend to it distinctive characteristics that make it a new article of manufacture, that is to say, the wood subjected to the foregoing treatment will be indurated, sterilized and rendered less hygroscopic and correspondingly immune from spores of fermentation or the like. And all these conditions are attained without checking, warping, case hardening or other deterioration of the physical characteristics of the wood.

By way of teaching the invention more in detail, one approved method of practising the same will be described with reference to the accompanying drawings, in which Figure I is a vertical longitudinal section of a container, suitable for carrying out the first five steps of the process.

Fig. II is a schematic View of the apparatus associated with the container for controlling it.

Fig. III is an end view, partly in section, of the container.

Fig. IV is a vertical longitudinal section of an equalizing chamber suitable for carrying out the last step of the process.

Igig. V is a section on the line 55, Fig.

Fig. VI is a plan "iew showing the various containers for the wood with the connecting means thereof for carrying out the several steps of the process.

1 represents a sterilizer of construction suitable for containing water at a temperature and under pressure considerably above the boiling point. 2 and 3 are uprights for firmly holding the lumber in proper position while being treated. It is also provided with heating coils 4, by which the temperature of the atmosphere, steam or water within the sterilizer may be heated to the desired degree; and with coils 5 which may be perforated for the purpose of supplying fle when desired. To equip the sterilizer 1 for conveniently developing the several conditions incident to the different steps of the process, it is provided with an exhaust pipe 6 leading to a vacuum pump 7 with an interposed condenser 8; a water supply pipe 9 that com municates with an uptake pipe 10 leading from an elevated water supply tank and also with a pump 11, by means of which water once supplied to the sterilizer 1 may be withdrawn and for the sake of economy, returned to the elevated tank for reuse. Water supplied through pipes 9 and 10 to the sterilizer 1 will proferably be previously heated and the coils 4 relied upon for maintaining its heat or raising it to the proper degree. The pipes 6, 9 and 10, as well as the connections with the return pump for the water, are provided with suitable valves to open and close them appropriately to the several steps of the process. 12 represents tracks to receive the car or truck upon which the lumber is loaded for introduction into the sterilizer.

Referring to Figs. IV and V, 13 represents the equalizing chamber which is preferably provided with heating pipes 14 preferably located at the bottom. This equalizing chamber is further provided with tracks 15 for convenient introduction of the charge of lumber, and its walls are preferably constructed so as to have a high co-efiicient of heat insulation for the sake of economy in operation. Referring to Fig. 6, 1 represents the sterilizer; 16 represents a boiler; 17 is the sweat chamber; 18 is a track extending through sweat chamber 17 and sterilizer 1 for the convenient introduction therethrough of a car load of lumber; 19 represents a transfer platform which is provided with a track 20 for the reception thereon of a car load of lumber; 21 is a track for the convenient introduction of a car of lumber into any one of the equalizing chambers 13; 22 are coaling chambers; 23 are tracks extending through equalizing chambers 13 and coaling chambers 22.

From the foregoing, it will be seen that the first essential condition to be produced is the thorough softening and opening up of the wood structure and the dissolving of its gummy sap matters and freeing them from their confinement, so that they can be distributed through the wood structure.

The equalizing step thoroughly and finally sets the resin through the wood piece, the resin having been equally distributed throughout the wood piece and permeated the cellular structure of the wood, been deposited in the form of a shellac upon the cell walls thereof and been diffused through the individual fibers thereof. Thus the wood will be dried and preserved by its own contained resinous properties, and this condition will have been attained without checking, warping or case hardening of the wood piece.

I claim 1. The process of extracting the fluid content of wood and substances contained there in, which consists in associating with the wood a heat radiating medium; then''sweating the wood; then subjecting the wood to a body of steam under pressure; then creating around the wood a partial vacuum; then submerging the wood in superheated water; then again creating a vacuum around the wood; then subjecting the wood to dry heat of high temperature; then subjecting the wood to a moderately heated, moist atmosphere.

2. The process of extracting the fluid content of wood and substances contained therein by subjecting the wood to steam under pressure; then submerging the wood in super-heated water alternated with a vacuum; then setting the resin in the wood by dry heat without pressure; finally cooling the wood in the presence of a moderately, heated, moist atmosphere. v

3. The process of extracting the fluid content of wood by surrounding the wood with steam until its pores are opened up; then creating a vacuum around the wood; then immersing the wood in super-heated water until its pores are opened up and its fiber softened; then subjecting it to a vacuum; then subjecting it to dry heat until the resins of the wood have thoroughly permeated the cellular structure thereof, and finally drying in a moderately heated moist atmosphere.

4. The process of extracting the fluid content of wood and substances contained therein, which consists in first associating with the wood a heat radiating material; then subjecting the wood to a moderately, heated moist atmosphere; then subjecting it to a saturated gaseous medium under pressure the said medium being at the boiling point of the fluid content of the wood which it is desired to extract until said medium has penetrated the wood; then submerging the wood in super-heated water alternated with a vacuum; then subjecting the wood to dry heat until the resinous properties of the wood have been uniformly distributed through the cellular structure of the wood.

5. The process of extracting the fluid content of wood and substances contained therein, consisting of sweating the wood; then subjecting it to steam under pressure; then submerging the wood in super-heated water; then creating a vacuum around the wood until sufficient internal vaporization has been produced to expel from the wood its fluid content and substances contained therein; then subjecting the wood to dry heat.

6. The process of extracting the fluid content of wood, which consists in subjecting the wood to a moderately heated, moist atmosphere; then subjecting it to a body of super-heated steam; then creating a partial vacuum around the wood; then submerging it in super-heated Water; then subjecting it to a gradual vacuum until suflicient internal vaporization has taken place in the wood to expel the fluid content thereof; then subjecting the wood to dry heat of a high temperature until the resinous properties of the wood have thoroughly permeated the cellular structure thereof and been difl'used through the fibers thereof, and finally cooling in the presence of a moderately, heated, moist atmosphere.

7. The process of extracting the fluid content of Wood and substances contained therein, which consists in first subjecting the Wood to a moderately, heated, moist atmosphere Without pressure; then subjecting the Wood to a body of steam; then producing around the Wood gradually a partial vacuum; then immersing the Wood in superheated Water; then again gradually creating a vacuum of greater intensity than the first named vacuum around the Wood until sufficient evaporation has taken place within the Wood piece to expel the fluid content and substances contained therein then subjecting it to dry heat until its resinous properties have been thoroughly distributed throughout the cellular structure thereof and set therein; finally harmonizin the internal temperature of the wood an the surrounding atmosphere.

8. The process of extracting the fluid content of wood, which consists in first sweating the wood; then subjecting it to a body of steam at a high temperature and under pressure; then immersing the wood in superheated water under pressure; then creating around the Wood a vacuum and simultaneously and gradually reducing the temperature until suflicient evaporation has taken place from the center of the wood to expel the fluid content thereof; then subjecting to dry heat of high temperature until the resins have thoroughly permeated the cellular structure thereof; finally harmonizing the internal temperature of the wood and a moderately heated atmosphere surrounding the Wood.

In testimony whereof I aflix my signature.

FREDERICK K, FISH, JR. 

